Gleeson also controversially argued that players should take into account disparities in size and weight when making quick decisions on the field.

When he cross-examined Naitanui, he asked the Eagles' star what he weighed and what he thought Amon weighed.

Naitanui replied 110kg for himself and about 80kg for Amon.

But Naitanui's counsel David Grace QC said the West Coast ruckman's tackle was not unreasonable and Amon's concussion might have happened because of other incidents during the game.

"I've tried my best to make sure that Amon didn't have my whole 110kg on his small frame," Naitanui said in his evidence, via a video link with Perth.

But Naitanui's defence suffered a blow when veteran Port Adelaide doctor Mark Fisher said several times in his evidence that he thought the tackle from the ruckman had caused Amon to suffer delayed concussion.

Fisher stuck to his argument under cross-examination from Grace.

Amon is in doubt for Saturday's Showdown clash with Adelaide because of the concussion.

The three-man jury took 15 minutes to decide the tackle was unreasonable and impact was medium - not low - meaning the one-game ban for Naitanui.

The hearing was delayed by a day because Grace had been unavailable.

Match review officer Michael Christian said on Tuesday that charging Naitanui was the easiest call he had made since taking over the role at the start of the season.

Eagles coach Adam Simpson said the decision to charge Naitanui was a head scratcher.

Early in the hearing, Grace asked that the tribunal jury should disregard Christian's comments.

His request prompted tribunal chairman David Jones to stress that the three-man jury was independent.

Jones made the comment again to jury members Richard Loveridge, David Neitz and Shane Wakelin at the end of the hearing, before they considered their verdict.